This study attempts to correlate clinical, pre- and postmortem physiological and postmortem findings in lungs from subjects with and without chronic airways obstruction. The postmortem methods include FEV1, isovolume pressure flow curves, frequency dependence of compliance, airway resistance and xenon 133 ventilation scans. The reversibility of increased small airway resistance in chronic airways obstruction has been found to be related to entrapped mucus plugs. These data are all correlated with each other and with the clinical and morphologic features of each case. We are also planning to study approximately 20 patients who are candidates for thoracotomy; preoperative tests include spirometry, closing volumes, maximum expiratory flow volume curves, frequency dependence of compliance and xenon 133 ventilation distribution studies. Lung biopsies obtained in these cases will be studied by light microscopy and electron microscopy and will provide fresh material for lung tissue culture. It is hoped that morphological validation of these physiological tests will be obtained.